甲醇钠引发的环氧乙烷开环聚合反应过程

运用密度泛函理论(DFT)的Dmol3方法, 计算了甲醇钠引发的环氧乙烷开环聚合的反应过程. 并运用前线轨道理论对该聚合反应的各步反应历程进行了分析. 计算结果表明, 链引发为无能垒的放热反应, 放出的能量达到92.560 kJ·mol-1, 而链增长过程则需越过100.951 kJ·mol-1的反应能垒, 链增长物种与环氧乙烷的前线轨道相对称, 可以使开环聚合反应继续进行下去. 当向反应体系中加入草酸、磷酸等质子酸时, 会立即发生链终止反应. 此外, 还对链增长过渡态的合理性进行了确认, 绘出了相应的反应势能曲线.

Ring-Opening Polymerization of Ethylene Oxide Initiated by Sodium Methoxide

The ring-opening polymerization process of ethylene oxide as initiated by sodium methoxide was studied using the density functional theory (DFT)/Dmol3method. Various steps of this polymerization reaction were analyzed by frontier orbital theory. For the chain initialization step, no energy barrier was apparent for the exothermic reaction and the energy released was 92.560 kJ·mol -1. The chain growth step needed to overcome a 100.951 kJ·mol-1 energy barrier. Frontier orbitals of chain growth species and those of ethylene oxide were similar and symmetric, so the ring-opening polymerization of ethylene oxide could occur smoothly. When adding a protonic acid, such as oxalic acid or phosphoric acid into the system, the polymerization chain growth would be terminated immediately. In addition, transition states were analyzed and confirmed while a potential energy diagram versus reaction coordinates was compiled for this polymerization process.